There are many systems that are designed to track the movement of an object or being. The field may be segmented into (a) systems that track movement outdoors, (b) systems that track movement indoors, and (c) systems that track movement indoors as well as outdoors. U.S. Pat. No. 5,225,842 is an example of the first case; U.S. Pat. No. 7,038,584 is an example of the second case; and U.S. Pat. No. 6,459,989 is an example of the third case.
Position tracking using GPS is a proven technology that works depending on the availability of positioning satellites. It fails when the device being tracked loses the satellite signals (i.e. enters a building or structure). Because of this failure an indoor positioning method must be used when in a GPS occluded environment.
Indoor tracking using RF technology is done in two different ways, timing (as described in U.S. Pat. No. 6,459,989) and received signal strength (as described in U.S. Pat. No. 6,720,922). Both of these technologies are dependent upon other RF nodes in the network and can only determine relative position between each other.
For indoor tracking to determine absolute position, at least three nodes in the network must have a known position. This problem has normally been solved by putting fixed position nodes indoors (as described in U.S. Pat. No. 5,977,913) or outdoors within range of the network (as described in U.S. Pat. No. 6,459,989). These solutions limit the range and mobility of the positioning system and require setup preparation before the system can be used to determine absolute position.
Mobile networking has become a practical solution with the development of Mobile Ad Hoc Networks (MANETs) and mesh networks (as described in U.S. Pat. No. 5,987,011). This type of networking can be used to create free roaming positioning systems with positioning communication.
As is apparent from above, no complete solution for a wireless mobile indoor/outdoor positioning system has been designed. While mobile outdoor positioning systems (as described in U.S. Pat. No. 7,050,819) and fixed indoor/outdoor positioning systems (as described in U.S. Pat. No. 6,459,989), have been developed, combining network mobility with indoor positioning to determine absolute position is undeveloped and the basis of this patent application.